You can try to delete search.sqlite and search.json in the Firefox Profile Folder

See also:

• http://kb.mozillazine.org/Search_Bar
• http://kb.mozillazine.org/Unable_to_search_or_add_new_engines

THE INFO ON THIS PAGE WORKED FOR ME WITH THE SAME PROBLEM. I HOPE IT HELPS YOU AS WELL . I USED THE ADD-ON TO LOCATE MY PROFILE FOLDER. DON'T FORGET TO CLOSE FIREFOX BEFORE DELETING THE SUGGESTED FILES. http://kb.mozillazine.org/Search_engines_disappear_from_Search_Bar

Uninstall Google toolbar, then re-install it. I have done this on two computers, and it fixed the problem.

EDIT : I had this problem too (see below) but restarting the computer cleared it (although previously restarting Iceweasel hadn't).

So... Cool.

Hi

I have this problem too, with Iceweasel 5.0 under Debian Squeeze.

Deleting search.sqlite and search.json or even formhistory.sql as suggested here and elsewhere did nothing.

Problem exists with all search engines (not just google) and I don't have the google toolbar.

Very annoying...